NavTech researchers said optimally "3 mins" w/the Type 92 mount's mechanical system, but this was rarely achieved as there were often problems w/reloading gear, and it might therefore become 20-30 mins.

Five (5) mins was the best reload time when done manually. This took a lot of manpower, however. At least ~10 men to get the torpedo into the tube by pulley instead of using the air motor, IIRC.

In the war under actual combat conditions I think you could find quite a lot of variation in times for reloading...although it was not required too often during battle.